Introducer assemblies for delivering implantable medical devices or for carrying medical tools such as measuring devices endovascular within a patient are well known. These assemblies enable introduction of the assembly into a patient from a convenient percutaneous entry point, often far from the treatment site. For example, entry via the femoral artery is commonly effected for treatments within the aorta.
In order to ensure that the introducer assembly can be reliably pushed through a patient's vasculature, it is important that the assembly does not kink or otherwise collapse during its use, yet it must be sufficiently flexible to be able to pass through tortuous vascular paths without damaging the vessel walls, as well as being trackable, typically over a guide wire. Catheters, sheaths and the like are prone to kinking, particularly when they are made to curve to tight radii. Moreover, in order not to adversely affect any components carried in the catheter, it is important that the catheter retains a stable inner lumen, particularly as it is pushed through the patient's vasculature and as it is made to curve.
In order to meet such performance requirements it is common to strengthen such catheters, metal strengthening elements being optimal given their elastic and strength/volume properties. It has been found, however, that metal strengthening elements act as antennae, which makes them unsuitable for use with measuring devices. Moreover, such strengthening elements can lead to heating of the sheath as a result of currents induced in the elements during imaging, in effect as a result of noticeable SAR (specific absorption rate) characteristics.
Examples of prior art catheter assemblies can be found, for example, in U.S. Pat. No. 6,273,876 and U.S. Pat. No. 7,909,812.
An attempt to avoid the heating effect prevalent in such sheath assemblies, a reflective coating has been disclosed in “Nano-Coated Implants Cut MRI Scan Dangers” by Duncan Graham-Rowe and Paul Marks in New Scientist, 1 Jun. 2003.